Objective: The following is a retrospective study on lower extremity alignment of rheumatoid arthritis (RA) patients with a history of both Total Hip Replacement (THR) and Total Knee Replacement (TKR).
Methods: From 1992 to 2000, our department had 26 rheumatoid arthritis patients who underwent both THR and TKR. We classified these patients into three groups based on radiographic alignment of the lower extremities in the standing position: Knock-knee (valgus deformity of the knees), Bowleg (varus deformity of the knees) and Windswept Deformity (one knee in severe varus alignment with the other in severe valgus alignment). Furthermore, we identified dominant weight bearing points of the hip as classified by the following new criteria: Central Shift, Lateral Shift, and Upward Shift. Mal-alignment was then evaluated based on these two classification systems.
Results: Of the 26 patients, 22 patients met our criteria and 4 did not. In mal-alignment, we had 11 cases in the knock-knee group, 5 cases in the bowleg group, and 6 cases in the Windswept deformity. Using the new criteria, central shift had 6 cases; lateral shift had 6 cases; and upward shift had 10 cases. The groups of Lateral shift and Central shift demonstrated deformities of the lower extremities were influenced by moving weight bearing points, pelvis obliquity, and adduction contractures of the hip joint. In upward shift, weight bearing lines did not change. Consequently, destruction of the joint in this group progressed symmetrically. Windswept deformity was asymmetric and had severe destruction on the other side of the knee and forefoot.
Discussion: Moving of weight bearing point, pelvis obliquity, and adduction contractures of the hip joint affected the severity of mal-alignment of the lower extremities.